This disclosure relates to a method of manufacturing an exhaust emission control device.
The removal of emissions, such as hydrocarbon, carbon monoxide, nitrogen oxide, particulate matter, and the like, from the exhaust gases of internal combustion engines enables cleaner operating vehicles. One focus area for such exhaust emission reduction has been in the area of post combustion control. Namely, post combustion control includes the placement of one or more exhaust emission control devices in the exhaust down stream of the internal combustion engine. Such exhaust emission control devices include catalytic converters, catalytic absorbers, diesel particulate traps, non-thermal plasma conversion devices, and the like.
Many exhaust emission control devices comprise a frangible or fragile structure that is prone to crushing and damage in the exhaust environment. For example, exhaust emission control devices have used a substrate, commonly comprising ceramic, cordierite, carbon, and the like, with a high surface area for exposing the substrate to the exhaust gas. In the example where exhaust emission control device is a catalytic converter, the substrate has a catalytically active material supported thereon.
During operation, the exhaust gases pass over the substrate and contact the catalyst where the amount of hydrocarbons, carbon monoxide, and oxides of nitrogen are reduced. The temperature of the catalyst is typically between 750xc2x0 C. and 950xc2x0 C., with about 350xc2x0 C. to about 450xc2x0 C. common for diesel exhausts, and may be higher depending upon the location of the catalytic converter relative to the engine of the automobile. To lessen the effects of this high temperature, a support material cushions and insulates the catalyst material from a housing in which the substrate and catalyst are mounted.
There are several common conventional methods for making exhaust emission control devices, the xe2x80x9cclamshellxe2x80x9d method, the xe2x80x9ctourniquetxe2x80x9d method, and the xe2x80x9cstuffedxe2x80x9d method. In the clamshell method, the internal end-cones and insulative material are cut to conform with each clamshell half, and the halves of the shell are assembled together by a welding process. The devices made by this method have reduced durability due to the poor control of the mat support material density.
The xe2x80x9ctourniquetxe2x80x9d method for forming a catalytic converter comprises wrapping the shell around the catalyst substrate and support mat assembly. The shell is formed by welding the edges while the assembly is squeezed at rated pressures calculated to optimize the support mat density. The end-cones are then welded to the shell assembly to form the catalytic converter. Although this method also has the disadvantages of increased cost due to the number of components that have to be processed and also the added cost of welding wires and gases, it claims improved mat density control.
The xe2x80x9cstuffedxe2x80x9d (with welded end-cone assemblies) method for forming a catalytic converter comprises wrapping the catalyst substrate in the insulative support material and stuffing it, under pressure, into a preformed typically round shell. The end-cone assemblies with the insulating material are fitted and welded to the shell assembly to form the catalytic converter. Conventional welding techniques have been commonly used to form these catalytic converters.
Conventional welding techniques involve the application of heat to localized areas of two metallic work pieces, which results in a uniting of the two work pieces. This type of welding may or may not be performed with the application of pressure, and may or may not include the use of a filler material. The drawbacks of conventional welding techniques include the creation of a high amount of heat that risks damage to the parts being welded. Another drawback is that dissimilar metals and work pieces of different gauge thicknesses cannot be joined, thereby limiting the materials used in forming catalytic converters. Lastly, these conventional techniques are expensive since they require a welding process that consumes welding wires and costly welding gases.
Accordingly, there remains a need in the art for a method for manufacturing a catalytic converter that is easily welded and cost effective.
Disclosed herein are methods for producing an exhaust emission control devices. In one embodiment, the method for manufacturing an exhaust emission control device comprises: disposing a first end around a second end, disposing an induction coil around the first end, discharging a current through the induction coil, forming eddy currents on the surface of the first end, and magnetic impulse sizing the first end and the second end together. The first end disposed around the second end comprises a tube end disposed around an end of an exhaust emission control device or the first end disposed around the second end comprises the exhaust emission control device end disposed around the tube end.
Another embodiment of a method for manufacturing an exhaust emission control device comprises disposing a substrate within a shell and disposing an induction coil around the shell, discharging a current through the induction coil, forming eddy currents on the surface of the shell, and magnetic impulse sizing or welding the shell about the substrate.
Another embodiment of a method for manufacturing an exhaust emission control device comprises disposing a substrate surrounded by a mat support material within a shell and disposing an induction coil around the shell, discharging a current through the induction coil, forming eddy currents on the surface of the shell, and magnetic impulse sizing the shell about the substrate.
Yet another embodiment of a method for manufacturing an exhaust emission control device comprises disposing a first end around a second end and disposing an induction coil around the first end, discharging a current through the induction coil, forming eddy currents on the surface of the first end, and magnetic impulse welding the first end and the second end together.